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During a recent severe geomagnetic storm on Earth, a rare and puzzling phenomenon was observed in the skies over Pennsylvania: orange auroras.
Captured by skywatcher Tony Bendele, these orange hues left scientists intrigued, as such colours are not typically associated with auroras. "At first, I thought something was wrong, so I checked this image numerous times. The colour orange is really there," Bendele remarked.
Auroras, or the northern and southern lights, are usually characterised by colors like green, pink, and red, resulting from the interaction of solar particles with specific atoms and molecules in Earth's atmosphere.
Green auroras are primarily due to oxygen, while pink ones are attributed to nitrogen. The mystery arises because there is no known atmospheric element that should produce a bright orange aurora.
Theoretically, nitrogen and oxygen can emit light at orange wavelengths, but these emissions are typically weak compared to other colors produced by the same molecules. Under normal circumstances, auroras should not appear orange.
However, during intense geomagnetic storms, such as the one on August 12, the usual separation between red and green auroras can blur. Red auroras, which occur at higher altitudes, and green auroras, which occur lower, can mix in a zone between 150 km to 200 km above the Earth's surface.
This overlap can create a yellow-orange glow, potentially explaining the mysterious orange auroras observed.
The geomagnetic storm responsible for this rare auroral display was triggered by a series of powerful solar eruptions known as coronal mass ejections (CMEs). These CMEs collide with Earth's magnetic field, funneling charged particles toward the poles and exciting atmospheric molecules, resulting in the auroras.
This event highlights the dynamic nature of space weather and its impact on Earth's atmosphere.
As solar activity continues to increase, scientists remain vigilant, studying these phenomena to better understand the complex interactions between solar particles and our planet's magnetic field.
